Excavators and the like, such as those used in public works and mining are used for pulling up, moving and loading earth and stones. These machines are usually provided with a shovel attached to a mechanical arm. The shovel is provided with a blade or beveled lip on a front edge intended for engaging and penetrating the mass of earth and stones. To prevent excessive wear of the blade and to aid penetrating the earth, it is common to assemble teeth associated with the blade projecting from the front edge thereof. However, said) teeth are also subjected to wear and breakages, so they must be frequently replaced, and furthermore, depending on the work that must be performed by the machine, it may be desirable to change the type or the shape of the teeth. To facilitate said replacement, tooth bar which are fixed to the blade of the shovel in a more or less permanent manner, and teeth are used, such that each tooth is releasably assembled in the tooth bar by means of a pin. Said pin usually traverses the orifices of the tooth and a duct traversing the tooth bar for the purpose of fixing the tooth to the tooth bar, thus assuring the connection between them using a retaining device for fixing said pin in its assembly position preventing the pin from coming out of its position when the machine is working and the tooth/tooth bar/pin system receives large stresses.
When the tooth and tooth bar assemblies work in difficult conditions, the pin attaching them tends to trove against the force for thrusting a retaining device which abort with the pin keep the tooth and the tooth bar attached. Then, the pin can come out of the tooth bar both the pin and the tooth may be lost. The loss of a tooth and/or pin may be very important depending on the work site thereof, possibly causing breakdowns in other machines, such as stone crushers, working in the same production site as the machine using the teeth, such as mines or quarries for example. As mentioned, a retaining device associated with the pin is used to prevent the pin from coming out of its assembly position between the tooth and the tooth bar, fixing the pin in its said assembly position. The retaining systems, comprising at least one pin and at least one retaining device, tend to have elastic features, provided to the retaining systems by the retaining device, so that the pin can be fixed and freed without requiring to break it while at the same time allowing its introduction into and extraction from the system in a simple, preferably hammerless manner, i.e., without needing a hammer.
Usually retaining devices made of elastic material such as rubber or polyurethane are used since it has elastic features which allow an easy to disassemble system, without applying excessive forces. These retaining devices are not useful for every type of works due to the fact that in applications where the temperature of the material moved, excavated or pulled up is high, the elastic material used can melt and/or lose its elastic qualities leaving the pin without retention, which could also cause a loss of the pin and/or of the tooth.
U.S. Pat. No. 3,952,433 describes a pin retaining system. The pin is introduced into aligned bores formed by the tooth and the tooth bar and the retaining device is provided with a clip in the form of a spring straddling the pin on both sides fixing it to its assembly position. Said clip is encapsulated in an elastomer element for the purpose of keeping said retaining element in its position.
Encapsulating the retaining system in an elastomeric element makes the retaining system useless in tasks where the working temperature is very high since the properties of the elastomer material are lost increasing the possibilities of losing the pin. Furthermore, the use of an elastomeric element causes interference problems between elements since it has an uncontrolled deformation by pressure. Another feature of this retaining system is that the use of a clip in combination with an elastomeric material, and the positioning of the assembly in the adaptor element, means that the force needed to be used for assembling and disassembling the pin is high, the use of a hammer being necessary and making it incompatible for hammerless systems.
The retaining system described in the U.S. Pat. No. 3,997,989 comprises a pin of variable sections and a retaining system provided with two spring's located in a washer shaped elastic element. The two springs of the retaining system have a straight area and a curved area of different section. Said washer with the two springs is positioned in a cavity in the adaptor element, then the tooth is assembled and then the pin, such that the section thereof causes the straight area of the springs to open being compressed until reaching notches located in the pin, and when the notches of the pin find the straight areas of the springs the latter are fixed in the notches preventing the pin from coming out. Like the U.S. Pat. No. 3,952,433, the use of an elastic material prevents this system from being used in works where the temperature is very high. Furthermore, the force needed for assembling and disassembling is high preventing its use in hammerless systems. Another drawback of this invention is that the retaining device, or washer, is located in a cavity which does not secure its position except at the time of coupling between the tooth and tooth bar.